CN112709308A

CN112709308A - Rainwater treatment method based on stepped garden

Info

Publication number: CN112709308A
Application number: CN202011507897.9A
Authority: CN
Inventors: 崔野; 宋长甫; 范永孟; 王作明; 魏平; 冯蕴哲; 牟巧玲; 王晓波
Original assignee: Real Estate Investment Co Ltd of China Railway 20th Bureau Group Co Ltd
Current assignee: Real Estate Investment Co Ltd of China Railway 20th Bureau Group Co Ltd
Priority date: 2020-12-18
Filing date: 2020-12-18
Publication date: 2021-04-27
Anticipated expiration: 2040-12-18
Also published as: CN112709308B; CN114941362A

Abstract

The invention discloses a rainwater treatment method based on a stepped garden, which adopts a multi-stage rainwater garden arranged in a stepped manner, introduces rainwater into the rainwater garden and flows through a high-grade rainwater garden and a low-grade rainwater garden in sequence to realize rainwater treatment. The invention can realize multiple rainwater treatment modes, can comprehensively remove pollutants such as COD, TN, TP, TSS and the like in rainwater, particularly has excellent effect on removing nitrogen (organic matters such as humus and the like mixed in the rainwater), enhances the removal capability of the rainwater garden on heavy metal ions such as Zn, Cd, Pb, Ni, Cr and the like, and enhances the rainwater retention capability, so that the rainwater garden rainwater system meets the requirements of mountain cities.

Description

Rainwater treatment method based on stepped garden

Technical Field

The invention relates to the technical field of rainwater gardens adopted in sponge city construction, in particular to a rainwater treatment method based on a stepped garden.

Background

The sponge city is a new generation of city rainfall flood management concept, and refers to a city which can be like a sponge and has good elasticity in the aspects of adapting to environmental changes, coping with natural disasters caused by rainwater and the like, and the city can also be called as a water elasticity city. The key factor is how to realize the treatment of rainwater in the sponge city construction.

The rainwater garden is a naturally formed or artificially excavated shallow-recessed green land, and is used for gathering and absorbing rainwater from a roof or the ground, purifying the rainwater through the comprehensive action of plants and sand, gradually permeating the rainwater into soil, conserving underground water, or supplementing urban water such as landscape water, toilet water and the like. The device is an ecological sustainable rain flood control and rain water utilization facility, and is widely applied to sponge city construction.

Chinese patent No. CN201711053691.1 discloses a method and structure for removing enhanced runoff pollution in a multi-stage rainwater garden in a sponge city, which utilizes the multi-stage rainwater garden to perform multi-stage treatment on pollutants in rainwater, specifically: rainwater flows into the first-stage rainwater garden through the water collecting tank and then flows into the second-stage rainwater garden, ammonia nitrogen organic matters in rainwater are firstly subjected to aerobic treatment in the first-stage rainwater garden and then converted into nitrate nitrogen, then subjected to anoxic/anaerobic treatment and converted into N2 to be discharged, untreated ammonia nitrogen organic matters enter the second-stage rainwater garden, and are firstly subjected to aerobic treatment in the second-stage rainwater garden and then converted into nitrate nitrogen, and then subjected to anoxic/anaerobic treatment and converted into N2 to be discharged; the insecticide in the rainwater is converted into small molecular substances after the anoxic/anaerobic treatment in the first-stage rainwater garden, and then enters the second-stage rainwater garden to be converted into pollution-free substances after the aerobic treatment. The scheme of this patent adopts multistage rainwater garden to carry out multistage processing to the pollutant, sets up the rainwater garden at different levels into the environment of upper oxygen boosting, lower floor oxygen deficiency/anaerobism, carries out the processing of good oxygen and oxygen deficiency/anaerobism to the pollutant many times to effectively get rid of the pollutant.

However, the prior art still has the following defects: 1 the rainwater permeates from top to bottom in gardens at all levels, the retention time of the rainwater is short, the treatment effect is poor, the rainwater cannot permeate underground in time, and the water storage effect of underground soil is not fully exerted. 2 the rainwater treatment modes in the gardens of all levels are aerobic-then-anaerobic treatment process flows, the treatment mode is single, the water treatment effect is poor, and meanwhile, the treatment effect is reduced due to the poor combination capacity of sewage and oxygen during aerobic treatment. 3 the rainwater garden has a common effect of removing main pollutants COD, TN, TP, TSS and the like and heavy metal ions Zn, Cd, Pb, Ni, Cr and the like in rainfall runoff of mountain cities such as Chongqing and the like.

Disclosure of Invention

Aiming at the defects of the prior art, the technical problems to be solved by the invention are as follows: how to provide a rainwater treatment method based on a stepped garden, which can improve the rainwater sewage treatment effect and better exert the underground soil water storage effect, and is more suitable for the requirement of sponge city construction.

In order to solve the technical problems, the invention adopts the following technical scheme:

a rainwater treatment method based on a stepped garden adopts a multi-stage rainwater garden arranged in a stepped manner, rainwater is led into the rainwater garden and flows through a high-grade rainwater garden and a low-grade rainwater garden in sequence to realize rainwater treatment.

In the scheme, the advancing direction of rainwater in the high-grade rainwater garden is changed, so that the rainwater flows from bottom to top. Therefore, the retention time of the rainwater in the garden is prolonged, and the treatment effect is improved. Meanwhile, rainwater can better penetrate into the underground, the water storage effect of underground soil can be better played, and the method is suitable for construction of sponge cities. Meanwhile, the rainwater flowing directions in the rainwater gardens at all levels are different, so that different water treatment processes can be formed more conveniently, and the overall water treatment effect is improved.

Wherein the filtration treatment comprises physical filtration and biochemical filtration. Thus, the water treatment effect can be improved more.

Further, set up heavy metal filtration structure in low-level rainwater garden bottom lowest and realize arranging to municipal rainwater pipeline after the heavy metal filters to the rainwater.

Therefore, heavy metal components mixed in the rainwater can be filtered better, and the rainwater filtering device is suitable for being used in industrialized cities.

Further, the method is realized by adopting a stepped garden device, the stepped garden device comprises at least two rainwater gardens which are arranged in a stepped manner, the rainwater garden at the upper part forms a high-grade rainwater garden, the rainwater garden at the lower part forms a low-grade rainwater garden, the rainwater garden is internally provided with filling materials, plants are planted on the upper surface of the rainwater garden, the high-grade rainwater garden is also internally provided with a vertical water inlet well, the upper end of the water inlet well is used for water inlet, and the lower end of the water inlet well is communicated with the bottom of the high-grade rainwater garden.

Therefore, when the stepped garden device is used, rainwater enters from the water inlet well, flows upwards from the bottom of the high-grade rainwater garden, falls from the upper part of the high-grade rainwater garden and enters the lower-grade rainwater garden below the high-grade rainwater garden, so that the detention time of the rainwater in the garden can be prolonged, the rainwater filtering effect is improved, and the rainwater can permeate underground.

Further, the bottom layer of the rainwater garden is a permeable concrete layer.

Therefore, rainwater can be more favorably infiltrated underground.

Furthermore, a gravel layer, a transition layer, a planting layer and a covering layer are sequentially arranged above the bottommost layer of the rainwater garden, the gravel layer is obtained by paving gravel, the transition layer is obtained by paving filler with the particle size smaller than that of the gravel, the planting layer is obtained by paving nutrient soil, the covering layer is made of biomass materials, and the lower end of the water inlet well is communicated with the gravel layer.

Therefore, after water enters, rainwater enters the gravel layer, and gaps between the gravel layers are large, so that the rainwater can be distributed uniformly and quickly after entering the gravel layer. Meanwhile, the rainwater forms a submerged area in the gravel layer to form an anoxic environment, which is favorable for growth and propagation of denitrifying bacteria and carries out biochemical filtration on the inflow water. The transition layer plays a transition role, and prevents the nutrient soil from falling into the gravel layer to cause blockage. The nutrient soil of the planting layer provides nutrients for the plants. The covering layer can avoid the loss of the nutrient soil layer.

Wherein, the gravel layer adopts gravel with the grain diameter of 3-5mm, the depth can be about 150mm, and the effect can be better ensured. The transition layer can adopt filler particles with high pores, is beneficial to the propagation of biochemical bacteria and improves the filtering effect, and can also adopt coarse sand with the particle size of 1-2, the cost is cheaper, the depth is about 150mm, and the effect can be better ensured. The depth of the planting layer can be about 500mm, and sufficient nutrition can be provided.

Preferably, the covering layer is prepared by mixing coconut shell particles and biological carbon particles, and more preferably, the biological carbon particles are prepared by pyrolyzing birch or birch bark serving as a raw material.

The structure of overburden like this can make the rainwater go into the overburden from the below better after, through coconut husk and biological carbon granule and air contact, forms the aerobic zone, is favorable to nitrobacteria's growth to breed. The coconut shell particles are internally of a high-density fibrous structure and have the characteristics of low porosity and high water absorption, so that the coconut shell particles have good retention performance on rainwater, can provide certain moisture for the growth of plants and the metabolism of bacteria during the alternation of dry and wet, ensure the removal effect of various nutrients by a system, and particularly provide guarantee for the continuous nitrification reaction of nitrobacteria under the drought condition. And the coconut shell particles are used as a light filter material with stable physical properties and have stronger corrosion resistance and decomposition resistance. Meanwhile, the biochar taking birch and birch bark as raw materials can also improve the adsorption and removal effects of the system on N, P and heavy metal ions. The biochar has high water conductivity and adsorption capacity due to a large amount of internal pore structure networks, and can also be an effective carrier for growth and adhesion of microorganisms, so that the pollutant treatment capacity of the system is improved, particularly, the biochar has a good adsorption removal effect on pollutants such as TN and TP and heavy metal ions such as Zn, Cd, Pb, Ni and Cr, and the pollutant removal performance of the rainwater garden is further ensured. Simultaneously, coconut husk granule and biological carbon particle mutually support, utilize the super hydroscopicity of coconut husk and biological carbon particle to the high adsorption volumetric capacity of air, can make in the covering rainwater can form good oxygen region with the air contact well under relative static environment, the coconut husk granule can also provide the living beings nitrogen source for good oxygen bacterium to do benefit to the growth and reproduction of good oxygen bacterium, make the rainwater realize good biochemical filter effect of nitration in the covering.

Furthermore, the biochar is prepared by pyrolyzing birch and birch bark serving as raw materials at the temperature of 380-420 ℃ for about 2 hours. Thus, the carbonization degree is just right, and the performance can be better ensured to reach the best.

Further, the volume ratio of the coconut shell particles to the biochar is 1: 2. the combination effect of the two materials can be better ensured to be optimal. The depth of the coating layer is about 100 mm.

And geotextile is arranged between the gravel layer and the transition layer.

Therefore, the soil can be better prevented from falling into the gravel layer, and the high pore structure of the gravel layer is ensured to be beneficial to forming the effect of a submerged area after the water inflow is converged.

Furthermore, a filter screen is arranged at the upper end of the water inlet well. And filtering out substances such as leaves and the like.

Furthermore, a net bag is arranged in the water inlet well, and a filtering filler is arranged in the net bag.

So can filter materials such as silt particle that mix with in the rainwater, avoid silt particle to get into the gravel layer and cause the jam, the filtration filler in the second income intake shaft can be favorable to anaerobic bacteria's reproduction, forms the anaerobism region in the intake shaft, consumes into the partial oxygen of water for the rainwater can form the oxygen deficiency region better after entering the gravel layer. The filtering filler is arranged in the net bag, which is beneficial to being lifted and cleaned after a period of time. The filtering filler is preferably porous biochemical filtering filler such as ceramsite.

Furthermore, a backflow pipeline is horizontally laid in a covering layer of the high-grade rainwater garden, a water inlet hole is formed in the backflow pipeline, a backflow pool is vertically arranged in the high-grade rainwater garden, a water outlet end of the backflow pipeline is connected into the backflow pool, the upper end of the backflow pool is sealed, a backflow pump is arranged at the bottom of the backflow pool, and an outlet end of the backflow pump is connected into a gravel layer of the high-grade rainwater garden through a pipeline.

Therefore, the arrangement of the return pipeline and the return pump can enable part of rainwater in the covering layer to flow back to the gravel layer, the covering layer is an aerobic area, and the rainwater treated by the nitrifying bacteria flows back to the gravel layer to provide a nitrogen source for denitrification in the gravel and provide conditions for establishment of a denitrification system in the gravel layer. Therefore, based on the structure of the advanced rainwater garden, the A20 sewage treatment process can be realized, namely rainwater enters through the water inlet well, an anaerobic section is formed in filler in the water inlet well, then the rainwater enters the gravel layer at the bottom of the rainwater garden to form an anoxic section, then the rainwater flows upwards in the rainwater garden and enters the upper end covering layer to form an aerobic section, part of rainwater in the aerobic section flows back to the gravel layer to provide a nitrogen source (nitrate) for denitrification reaction of denitrifying bacteria in the anoxic section, so that the rainwater is firstly subjected to anaerobic bacteria reaction treatment in the anaerobic section, then subjected to denitrification reaction treatment of denitrifying bacteria in the anoxic section, and then flows out after the nitrification reaction treatment is realized by nitrifying bacteria in the aerobic section. Thus, the A20 sewage treatment process is realized, the excellent synchronous denitrification and dephosphorization effect is achieved, the water treatment effect can be greatly improved, and especially the removal effect on nitrogen pollutants in rainwater is improved.

Furthermore, the outlet end of the reflux pump in the reflux pool is connected to the gravel layer of the high-grade rainwater garden through a reflux water distribution pipeline, and the reflux water distribution pipeline is provided with water distribution holes.

In this way, the returning rainwater can be more evenly distributed into the gravel layer.

Furthermore, a one-way air valve is arranged at the upper end of the backflow pool.

Therefore, the sealing effect of the backflow pool can be ensured, and oxygen is prevented from entering backflow rainwater. Meanwhile, the one-way air valve can release gas generated by biochemical reaction in the backflow tank, so that potential safety hazards are reduced.

Further, still be provided with an overflow pipe in the backward flow pond, the vertical setting of overflow pipe and the open end on upper portion are located backward flow pond upper portion, and the overflow pipe lower extreme links to each other with municipal rainwater pipeline.

Like this, when the backward flow rainwater was too much in the backward flow pond, can arrange toward municipal rainwater pipe network through the overflow pipe.

Furthermore, a water collecting structure is further arranged in the covering layer of the high-grade rainwater garden, the water collecting structure comprises a plurality of water collecting pipes which are arranged along the direction perpendicular to the low-grade rainwater garden and are arranged in parallel at intervals, the water distributing pipes are also wrapped at the edge positions of one side of the high-grade rainwater garden and one side of the low-grade rainwater garden, the water collecting pipes are communicated with the water distributing pipes, a plurality of water inlet holes are formed in the water collecting pipes, and a plurality of water distributing holes are formed in the suspended side of the water distributing pipes.

Therefore, the rainwater in the high-grade rainwater garden covering layer is collected by the water collecting pipe and distributed by the water distributing pipe, so that the rainwater falls from the air through the water distributing holes and enters the low-grade rainwater garden. Therefore, the landscape effect similar to a water curtain can be formed, rainwater can fully contact with air and then enter the low-grade rainwater garden, an aerobic area is better formed in the upper area of the low-grade rainwater garden, nitrification reaction treatment is further carried out, and the defect that the nitrification treatment effect of a static aerobic area at the upper end of the high-grade rainwater garden is possibly insufficient is overcome. Meanwhile, after rainwater enters the low-level rainwater garden, an upper aerobic area and a lower anaerobic area are sequentially formed from top to bottom, and the rainwater is subjected to nitrification and denitrification filtration treatment again. Therefore, the high-grade rainwater garden and the low-grade rainwater garden jointly act, so that rainwater passes through multiple different biochemical filtering treatment flows, and the integral biochemical filtering treatment effect on the rainwater is greatly improved.

Furthermore, a permeable geotextile is wrapped on the water collecting pipe. Therefore, the geotextile can better absorb water and collect water, and can prevent solid particles from entering a water collecting pipe.

Furthermore, the lowest part of the bottom of the low-level rainwater garden is provided with a discharge pipeline connected with a municipal rainwater pipeline, and the inlet end of the discharge pipeline is also provided with a heavy metal filtering filter element.

Therefore, heavy metal pollutants in rainwater can be further filtered, and the comprehensive rainwater filtering treatment effect in industrial cities is guaranteed.

Furthermore, the upper surface of the low-level rainwater garden is also provided with an overflow sewer which is connected with a municipal rainwater pipeline. Therefore, redundant rainwater can be collected when the rainwater amount is large, and overflowing is avoided.

In conclusion, the invention can realize multiple rainwater treatment modes, can comprehensively remove pollutants such as COD, TN, TP, TSS and the like in rainwater, particularly has excellent effect on removing nitrogen (organic matters such as humus and the like mixed in the rainwater), enhances the removal capability of heavy metal ions such as Zn, Cd, Pb, Ni, Cr and the like in a rainwater garden and enhances the rainwater retention capability, and is suitable for the requirements of mountain cities.

Drawings

Fig. 1 is a schematic top view of the present invention.

Fig. 2 is a cross-sectional view of fig. 1 taken along the longitudinal direction.

Fig. 3 is a cross-sectional view of fig. 1 in the transverse direction.

Fig. 4 is a schematic structural view of a single water collecting pipe and a water distributing pipe in fig. 1.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

In the specific implementation: a rainwater treatment method based on a stepped garden adopts a multi-stage rainwater garden arranged in a stepped manner, rainwater is led into the rainwater garden and flows through a high-grade rainwater garden and a low-grade rainwater garden in sequence to realize rainwater treatment.

During implementation, the heavy metal filtering structure is arranged at the lowest position of the bottom of the low-level rainwater garden, so that heavy metal is filtered by rainwater and then is discharged to the municipal rainwater pipeline.

Referring to fig. 1-4 (arrows indicate the flowing direction of rainwater), the method is realized by using a stepped garden device, the stepped garden device comprises at least two rainwater gardens which are arranged in a stepped manner, the rainwater garden at the upper part forms a high-grade rainwater garden 1, the rainwater garden at the lower part forms a low-grade rainwater garden 2, the rainwater gardens are internally provided with fillers, plants 3 are planted on the upper surface of the rainwater garden, the high-grade rainwater garden is also provided with a vertical water inlet well 4, the upper end of the water inlet well 4 is used for water inlet, and the lower end of the water inlet well is communicated with the bottom of the high-grade rainwater garden.

Therefore, when the stepped garden device is used, rainwater enters from the water inlet well, flows upwards from the bottom of the high-grade rainwater garden, falls from the upper part of the high-grade rainwater garden and enters the lower-grade rainwater garden below the high-grade rainwater garden, so that the detention time of the rainwater in the garden can be prolonged, the rainwater filtering effect is improved, and the rainwater can permeate underground. Still be provided with into water overflow pipe in the well during implementation, the rainwater is too much to be discharged to municipal administration rainwater pipeline through overflow pipe when not handling.

Wherein, the lowest layer of the rainwater garden is a permeable concrete layer 5.

Therefore, rainwater can be more favorably infiltrated underground.

The upper part of the lowest layer of the rainwater garden is sequentially provided with a gravel layer 6, a transition layer 7, a planting layer 8 and a covering layer 9, the gravel layer 6 is obtained by paving gravel, the transition layer 7 is obtained by paving filler with the particle size smaller than that of the gravel, the planting layer 8 is obtained by paving nutrient soil, the covering layer 9 is made of biomass material, and the lower end of the water inlet well is communicated with the gravel layer.

Wherein, the gravel layer 6 is preferably gravel with the particle size of 3-5mm, and the depth can be about 150mm, so that the effect can be better ensured. The transition layer can adopt filler particles with high pores, is beneficial to the propagation of biochemical bacteria and improves the filtering effect, and can also adopt coarse sand with the particle size of 1-2, the cost is cheaper, the depth is about 150mm, and the effect can be better ensured. The depth of the planting layer can be about 500mm, and sufficient nutrition can be provided.

In practice, the filler of the planting layer 8 can be composed of 7% of fly ash and 93% of sandy soil.

Therefore, the rainwater garden can ensure the removal effect of TN, TP and COD on the premise that the rainwater permeability coefficient meets the requirement (100-300 mm/h), so that the rainwater garden can be more suitable for the requirement of mountain cities.

In practice, the covering layer 9 is prepared by mixing coconut shell particles and biochar particles, and more preferably, the biochar particles are prepared by pyrolyzing birch or birch bark serving as a raw material.

Wherein the biochar is prepared by pyrolyzing birch and birch bark serving as raw materials at the temperature of 380-420 ℃ for about 2 h. Thus, the carbonization degree is just right, and the performance can be better ensured to reach the best.

Wherein, the volume ratio of the coconut shell particles to the biochar is 1: 2. the combination effect of the two materials can be better ensured to be optimal. The depth of the coating layer is about 100 mm.

Wherein, a geotextile 10 is arranged between the gravel layer 6 and the transition layer 7.

Wherein, the upper end of the water inlet well 4 is provided with a filter screen 11. And filtering out substances such as leaves and the like.

Wherein, a net bag (not shown in the figure) is arranged in the water inlet well 4, and a filtering filler 12 is arranged in the net bag.

So can filter materials such as silt particle that mix with in the rainwater, avoid silt particle to get into the gravel layer and cause the jam, the filtration filler in the second income intake shaft can be favorable to anaerobic bacteria's reproduction, forms the anaerobism region in the intake shaft, consumes into the partial oxygen of water for the rainwater can form the oxygen deficiency region better after entering the gravel layer. The filtering filler is arranged in the net bag, which is beneficial to being lifted and cleaned after a period of time. Wherein the filtering filler is preferably porous biochemical filtering filler such as ceramsite; or may be arranged similarly to the padding in a rain garden.

Wherein, a backflow pipeline 13 is horizontally laid in the covering layer of the high-grade rainwater garden, a water inlet hole is arranged on the backflow pipeline 13, a backflow pool 14 is vertically arranged in the high-grade rainwater garden, the water outlet end of the backflow pipeline 14 is connected into the backflow pool 14, the upper end of the backflow pool 14 is sealed, a backflow pump 15 is arranged at the bottom of the backflow pool, and the outlet end of the backflow pump is connected into the gravel layer of the high-grade rainwater garden through a pipeline.

Wherein, the outlet end of a reflux pump 15 in the reflux pool is connected to the gravel layer of the high-grade rainwater garden through a reflux water distribution pipeline 16, and the reflux water distribution pipeline 16 is provided with water distribution holes.

Wherein, the upper end of the backflow pool is also provided with a one-way air valve 17.

Wherein, still be provided with an overflow pipe 18 in the backward flow pond, the vertical setting of overflow pipe and the open end on upper portion are located backward flow pond upper portion, and the overflow pipe lower extreme links to each other with municipal rainwater pipeline.

The covering layer of the high-grade rainwater garden is also provided with a water collecting structure, the water collecting structure comprises a plurality of water collecting pipes 19 which are arranged along the direction perpendicular to the direction of the low-grade rainwater garden and are arranged in parallel at intervals, the water distributing pipe 20 which is positioned at the edge position of one side of the high-grade rainwater garden adjacent to the low-grade rainwater garden is also wrapped, the water collecting pipes 19 are communicated with the water distributing pipes 20, the water collecting pipes are provided with a plurality of water inlet holes, and one suspended side of the water distributing pipes is provided with a plurality of water distributing holes.

Wherein, the catchment pipe 19 is wrapped with a permeable geotextile. Therefore, the geotextile can better absorb water and collect water, and can prevent solid particles from entering a water collecting pipe.

Wherein, the lowest position of the bottom of the low-level rainwater garden 2 is provided with a discharge pipeline which is connected with a municipal rainwater pipeline, and the inlet end of the discharge pipeline is also provided with a heavy metal filtering filter element 21.

Wherein, the upper surface of the low-level rainwater garden is also provided with an overflow sewer 22, and the overflow sewer 22 is connected with a municipal rainwater pipeline. Therefore, redundant rainwater can be collected when the rainwater amount is large, and overflowing is avoided.

In addition, the plants to be planted can be windmill grass and canna.

Therefore, the windmill grass is a deep-rooted plant with flooding resistance and drought resistance and developed root system, the developed root part of the windmill grass not only can provide sufficient attachment points for microorganisms in soil, but also can provide certain oxygen for nitration reaction of nitrobacteria through the oxygen secretion function of the root system, and the permeability of the soil to rainwater can be enhanced. Meanwhile, the glass has a certain ornamental value and is relatively low in cost. Canna has good pollutant removal performance on rainwater, and can make up for the defect of insufficient ornamental value of pinwheel grass to a certain extent.

The maintenance of the garden equipment system is divided into regular and irregular maintenance.

And (3) regular maintenance: including regular harvesting of plants and cleaning of the waste on the surface of the rain garden, the shallow filter material on the surface of the garden can be replaced as necessary to maintain normal treatment performance. The permeable geotextile of the rainwater garden should be checked regularly for blockage, and if the blockage occurs, the geotextile should be replaced in time.

Irregular maintenance: the method comprises the steps of irrigating at irregular time in a drought period and checking the growth condition of plants, if the growth condition of the plants is found to be not good, replacing the vegetation types in time after other possibilities are eliminated, and ensuring that the normal operation of the system is not influenced.

During implementation, the water inlet well can be connected with a roof rainwater drainage pipe, so that rainwater collected by the rainwater garden is mainly sourced from roof rainwater, and the water inlet and the one-level flower bed are integrally designed, so that the rainwater garden has both attractiveness and practicability. In addition, the water pipe at the bottom of the low-level rainwater garden can be finally connected to catchment facilities such as a community reservoir or a fountain and the like during implementation, so that the rainwater garden further enhances the sponge property of the community while purifying the rainwater on the roof, and effectively reduces the probability of waterlogging of the community.

Claims

1. A rainwater treatment method based on a stepped garden adopts a multi-stage rainwater garden arranged in a stepped manner, rainwater is led into the rainwater garden and flows through a high-grade rainwater garden and a low-grade rainwater garden in sequence to realize rainwater treatment.

2. A method of treating stepped garden based stormwater as claimed in claim 1, wherein the filtration treatment includes physical and biochemical filtration.

3. The method for treating rainwater based on a stepped garden as claimed in claim 2, wherein a heavy metal filtering structure is provided at the lowest part of the bottom of the low-grade rainwater garden to filter heavy metals of rainwater and then discharge the rainwater to the municipal rainwater pipe.

4. The method for treating rainwater based on stepped gardens as claimed in claim 1, wherein the method is implemented by using a stepped garden device comprising at least two rainwater gardens arranged in steps, the rainwater garden located at the upper part forms a high-grade rainwater garden, the rainwater garden located at the lower part forms a low-grade rainwater garden, the rainwater garden is internally provided with filling materials, plants are planted on the upper surface of the rainwater garden, the high-grade rainwater garden is also provided with a vertical water inlet well, the upper end of the water inlet well is used for water inlet, and the lower end of the water inlet well is communicated with the bottom of the high-grade rainwater garden.

5. A method of stormwater treatment over a stepped garden as claimed in claim 4, wherein the lowest layer of the stormwater garden is a layer of pervious concrete.

6. A method of stormwater treatment as claimed in claim 4, wherein the stormwater garden has above its lowermost floor, in that order, a gravel layer, a transition layer, a planting layer and a covering layer, the gravel layer being formed by gravel placement, the transition layer being formed by a packing material having a particle size smaller than that of the gravel, the planting layer being formed by nutrient soil placement, the covering layer being formed of a biomass material, and the lower end of the entry well being in communication with the gravel layer.

7. A method of treating stormwater according to claim 6, wherein the cover is made of a mixture of coconut shell particles and biochar particles;

the biochar is prepared by pyrolyzing birch and birch bark serving as raw materials at the temperature of 380-420 ℃ for 2 h;

the volume ratio of the coconut shell particles to the biochar is 1: 2;

and geotextile is arranged between the gravel layer and the transition layer.

8. A method for treating rainwater based on a stepped garden as claimed in claim 4, wherein the upper end of the water inlet well is provided with a filter screen;

a net bag is arranged in the water inlet well, and a filtering filler is arranged in the net bag.

9. The method for treating rainwater based on the stepped garden as claimed in claim 4, wherein a backflow pipe is further horizontally laid in the covering layer of the advanced rainwater garden, a water inlet is formed in the backflow pipe, a backflow pool is further vertically arranged in the advanced rainwater garden, the water outlet end of the backflow pipe is connected into the backflow pool, the upper end of the backflow pool is sealed, a backflow pump is arranged at the bottom of the backflow pool, and the outlet end of the backflow pump is connected into the gravel layer of the advanced rainwater garden through a pipeline;

the outlet end of a reflux pump in the reflux pool is connected into a gravel layer of the advanced rainwater garden through a reflux water distribution pipeline, and a water distribution hole is formed in the reflux water distribution pipeline;

the upper end of the backflow pool is also provided with a one-way air valve;

still be provided with an overflow pipe in the backward flow pond, the vertical setting of overflow pipe and the open end on upper portion are located backward flow pond upper portion, and the overflow pipe lower extreme links to each other with municipal rainwater pipeline.

10. The method for treating rainwater based on a stepped garden as claimed in claim 4, wherein the covering layer of the high-grade rainwater garden is further provided with a water collection structure, the water collection structure comprises a plurality of water collection pipes which are arranged along the direction perpendicular to the low-grade rainwater garden and are arranged in parallel at intervals, the water distribution pipes are further wrapped at the edge positions of one side of the high-grade rainwater garden and the low-grade rainwater garden which are adjacent to each other, the water collection pipes are communicated with the water distribution pipes, the water collection pipes are provided with a plurality of water inlet holes, and the suspended side of the water distribution pipes is provided with a plurality of water distribution holes;

the lowest position of the bottom of the low-level rainwater garden is provided with a discharge pipeline which is connected with a municipal rainwater pipeline, and the inlet end of the discharge pipeline is also provided with a heavy metal filtering filter element.